A wireless network node uses an antenna to exchange signals with wireless devices. To improve capacity, the wireless network node may be configured with multiple antennas per sector, such as 2, 4, or 8 antennas. The spectrum available for the antennas may be limited. For example, for frequencies between 0.05 to 3 GHz, spectrum is typically allocated in 20 to 70 MHz bands, and the bands are typically licensed and shared among many operators in blocks from 5 to 20 MHz. Frequency reuse is typically set to one, which means that all spectrum is reused in all sectors/sites. Using a high number of antennas in a limited spectrum environment tends to create interference due to the spatial reuse of the spectrum. The interference limits the data rates of the system and degrades system performance.
The demand for larger capacity and higher data rates in wireless communication systems necessitates the need for wider bandwidth and significant additional spectrum. This is available only at higher frequencies than currently in use. In order to transmit and receive at higher frequencies, beamforming is needed in order to achieve reasonable link budgets.